Acceleration in the plasma focus and in astrophysics

Author:

Browne P. F.

Abstract

Both, in the laboratory (specifically the plasma focus) and in astrophysics, charges are accelerated in magnetically pinched current channels. The current channels are annular cylinders, defined by an electric double layer of thickness δrE and radius R due to radial polarization of the plasma. The electric field Er in the double layer and the azimuthal magnetic field Bϕ ensure drifts of charges in the axial direction, but ions do not take up the full drift velocity because their Larmor radius exceeds δrE. Magnetic pinching of the channel reduces the cross sectional area S, and an instability of drift velocity may denude a region of current channel. The inductively maintained current J then cannot be carried by free charges, even with relativistic drift velocity. A displacement current (S/4π) δEzt arises, Ez growing until all energy in Bϕ is transferred into Ez. During this transfer Bϕ decreases, so the pinch weakens, permitting discharge of accumulated space charge via a conduction current without reversal of J. Thereafter the cycle repeats quasi-periodically.In astrophysics acceleration occurs in a pinched magnetic vortex tube (MVT). The difference is that now Bϕ(r, +z) = −Bϕ(r, −z) due to winding of loops of field lines. Hence J reverses across mid-pinch, which implies accumulation of space charge of one sign at mid-pinch and of opposite sign at the ends of the pinch. Now there is reversal of J when the space charge relaxes.

Publisher

Hindawi Limited

Subject

Electrical and Electronic Engineering,Condensed Matter Physics,Atomic and Molecular Physics, and Optics

Cited by 5 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. The International Year of Astronomy;Laser and Particle Beams;2009-05-05

2. Double-layer pulse current model for the plasma focus;Plasma Physics and Controlled Fusion;1994-06-01

3. Active Galactic Nuclei: Their Synchrotron and Cerenkov Radiations;Progress in New Cosmologies;1993

4. An electrodynamical model for the ion behaviour in the final plasma focus stages;Plasma Physics and Controlled Fusion;1992-08-01

5. Dynamic Electric Fields and Double Layers in Laser-Produced Plasmas;Fusion Technology;1989-12

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